This invention relates in general to eccentric-spider tine-orientation control assemblies for reel-type harvesting machinery having a pick-up reel which rotates about a horizontal axis and which, as the machine moves through a field of grain, grasses or other similar crops, is rotatably driven to gather the crop and feed it to a cutter bar for severing the crop from the stubble at ground level.
The operation of prior art eccentric tine-orientation control assemblies for maintaining pick-up tine at predetermined orientation as the reel rotates is based on the kinematics of the parallelogram four-bar linkage wherein opposite links of each pair of links of the linkage are of equal length. The basic difficulty in the application of the parallelogram four-bar linkage to the design of prior art tyne-orientation control assemblies for harvesters lies in the undesirability from a manufacturing standpoint of having to match selectively four-bar linkage assembly links having differing manufacturing dimensional tolerances such as are necessary to make the part on an economical basis. Unless comprised of selectively matched or loosely assembled links when the four-bar linkage passes through top and bottom center configurations, the tolerance build-up in one pair of links as pinned in straightline end-to-end configuration fights the tolerance build-up in the other pair of links also pinned end-to-end in like straightline configuration and assembled thereto. As a result, very high locked-up loads are generated in the pin joints of the parallelogram four-bar linkage. Such loads are conducive to high wear on the pin joints and shortening of life of the same.
Attempts to relieve these locked-up loads by adding an additional link to the parallelogram-type four-bar linkage tine-orientation control assembly have in the past been thwarted because the five-bar linkage so produced is a kinematically unstable configuration.
There is thus an established need for a stable tine orientation control assembly for a harvester reel which has lower peak loads and less sensitivity to dimensional tolerance stack-up in the assembly of working parts thereof for reducing the wear thereon and increasing the life of the bearings and casting ring races incorporated therein.